Patient Transport Apparatus With Auxiliary Wheel System

ABSTRACT

A patient transport apparatus transports a patient over a floor surface. The patient transport apparatus comprises a support structure and support wheels coupled to the support structure. An auxiliary wheel is coupled to the support frame to influence motion of the patient transport apparatus over a floor surface. The auxiliary wheel is movable to a deployed position with the auxiliary wheel engaging the floor surface and a stowed position with the auxiliary wheel spaced a distance from the floor surface. An actuator assembly including a lift actuator a biasing device, and a biasing load adjustment assembly. The lift actuator is operable to move the auxiliary wheel to the deployed position and to the stowed position. The biasing device configured to bias the auxiliary wheel towards the deployed position. The biasing load adjustment assembly configured to adjust a biasing force being applied by the biasing device to the auxiliary wheel.

CROSS-REFERENCE TO RELATED APPLICATIONS

The subject patent application is a Continuation of U.S. patentapplication Ser. No. 17/695,132 filed on Mar. 15, 2022, which is aContinuation of U.S. patent application Ser. No. 16/690,227 filed onNov. 21, 2019 and issued as U.S. Pat. No. 11,304,860 on Apr. 19, 2022,which claims priority to and all the benefits of U.S. Provisional PatentApplication No. 62/770,442 filed on Nov. 21, 2018, the disclosures ofeach of which are hereby incorporated by reference in their entirety.

BACKGROUND

Patient transport systems facilitate care of patients in a health caresetting. Patient transport systems comprise patient transportapparatuses such as, for example, hospital beds, stretchers, cots,tables, wheelchairs, and chairs to move patients between locations. Aconventional patient transport apparatus comprises a base, a patientsupport surface, and several support wheels, such as four swivelingcaster wheels. Often, the patient transport apparatus has an auxiliarywheel system that includes one or more non-swiveling auxiliary wheels,in addition to the four caster wheels. The auxiliary wheel, by virtue ofits non-swiveling nature, is employed to help control movement of thepatient transport apparatus over a floor surface in certain situations.

When a caregiver wishes to use the auxiliary wheel to help controlmovement of the patient transport apparatus, such as down long hallwaysor around corners, the caregiver operates an actuator assembly toselectively move the auxiliary wheel from a stowed position, out ofcontact with the floor surface, to a deployed position in contact withthe floor surface. In addition, at least some known auxiliary wheelsystems may include a biasing device that acts upon the auxiliary wheelto bias the auxiliary wheel downwardly toward the floor surface tomaintain traction between the auxiliary wheel and the floor surface. Inmany cases, it's desirable to service the auxiliary wheel system formaintenance and repair. However, a service technician must safely removethe biasing device before performing maintenance on the actuatorassembly and/or auxiliary wheel. The safe removal of these biasingdevices may be time consuming and labor intensive, thus increasing thecost of maintaining known auxiliary wheel systems.

A patient transport apparatus designed to overcome one or more of theaforementioned challenges is desired.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a patient transport apparatus.

FIG. 2 is a perspective view of an auxiliary wheel assembly of thepatient transport apparatus coupled to a base of the patient transportapparatus.

FIG. 3A is a perspective view of the auxiliary wheel assembly comprisingan auxiliary wheel and a lift actuator.

FIG. 3B is a plan view of the auxiliary wheel assembly comprising theauxiliary wheel and the lift actuator.

FIG. 4 is an elevational view of the auxiliary wheel in a firstposition.

FIG. 5 is an elevational view of the auxiliary wheel in a secondposition.

FIG. 6 is an elevational view of the auxiliary wheel in a thirdposition.

FIGS. 7-10 are perspective views of the auxiliary wheel assemblycomprising a biasing load adjustment assembly.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Referring to FIG. 1 , a patient transport system comprising a patienttransport apparatus 20 is shown for supporting a patient in a healthcare setting. The patient transport apparatus 20 illustrated in FIG. 1comprises a hospital bed. In other embodiments, however, the patienttransport apparatus 20 may comprise a cot, table, wheelchair, chair, orsimilar apparatus, utilized in the care of a patient to transport thepatient between locations.

A support structure 22 provides support for the patient. The supportstructure 22 illustrated in FIG. 1 comprises a base 24 and anintermediate frame 26. The base 24 defines a longitudinal axis 28 from ahead end to a foot end. The intermediate frame 26 is spaced above thebase 24. The support structure 22 also comprises a patient support deck30 disposed on the intermediate frame 26. The patient support deck 30comprises several sections, some of which articulate (e.g., pivot)relative to the intermediate frame 26, such as a fowler section, a seatsection, a thigh section, and a foot section. The patient support deck30 provides a patient support surface 32 upon which the patient issupported.

A mattress, although not shown, may be disposed on the patient supportdeck 30. The mattress comprises a secondary patient support surface uponwhich the patient is supported. The base 24, intermediate frame 26,patient support deck 30, and patient support surface 32 each have a headend and a foot end corresponding to designated placement of thepatient's head and feet on the patient transport apparatus 20. Theconstruction of the support structure 22 may take on any known orconventional design, and is not limited to that specifically set forthabove. In addition, the mattress may be omitted in certain embodiments,such that the patient rests directly on the patient support surface 32.

Side rails 38, 40, 42, 44 are supported by the base 24. A first siderail 38 is positioned at a right head end of the intermediate frame 26.A second side rail 40 is positioned at a right foot end of theintermediate frame 26. A third side rail 42 is positioned at a left headend of the intermediate frame 26. A fourth side rail 44 is positioned ata left foot end of the intermediate frame 26. If the patient transportapparatus 20 is a stretcher, there may be fewer side rails. The siderails 38, 40, 42, 44 are movable between a raised position in which theyblock ingress and egress into and out of the patient transport apparatus20 and a lowered position in which they are not an obstacle to suchingress and egress. The side rails 38, 40, 42, 44 may also be movable toone or more intermediate positions between the raised position and thelowered position. In still other configurations, the patient transportapparatus 20 may not comprise any side rails.

A headboard 46 and a footboard 48 are coupled to the intermediate frame26. In other embodiments, when the headboard 46 and footboard 48 areprovided, the headboard 46 and footboard 48 may be coupled to otherlocations on the patient transport apparatus 20, such as the base 24. Instill other embodiments, the patient transport apparatus 20 does notcomprise the headboard 46 and/or the footboard 48.

User interfaces 50, such as handles, are shown integrated into thefootboard 48 and side rails 38, 40, 42, 44 to facilitate movement of thepatient transport apparatus 20 over floor surfaces. Additional userinterfaces 50 may be integrated into the headboard 46 and/or othercomponents of the patient transport apparatus 20. The user interfaces 50are graspable by the user to manipulate the patient transport apparatus20 for movement.

Other forms of the user interface 50 are also contemplated. The userinterface 50 may simply be a surface on the patient transport apparatus20 upon which the user logically applies force to cause movement of thepatient transport apparatus 20 in one or more directions, also referredto as a push location. This may comprise one or more surfaces on theintermediate frame 26 or base 24. This could also comprise one or moresurfaces on or adjacent to the headboard 46, footboard 48, and/or siderails 38, 40, 42, 44.

In the embodiment shown, one set of user interfaces 50 comprises a firsthandle 52 and a second handle 54. The first and second handles 52, 54are coupled to the intermediate frame 26 proximal to the head end of theintermediate frame 26 and on opposite sides of the intermediate frame 26so that the user may grasp the first handle 52 with one hand and thesecond handle 54 with the other. In other embodiments, the userinterfaces 50 comprise one or more of a joystick, dial, or knob in placeof the first and second handles 52, 54.

Support wheels 56 are coupled to the base 24 to support the base 24 on afloor surface such as a hospital floor. The support wheels 56 allow thepatient transport apparatus 20 to move in any direction along the floorsurface by swiveling to assume a trailing orientation relative to adesired direction of movement. In the embodiment shown, the supportwheels 56 comprise four support wheels each arranged in corners of thebase 24. The support wheels 56 shown are caster wheels able to rotateand swivel about swivel axes 58 during transport. Each of the supportwheels 56 forms part of a caster assembly 60. Each caster assembly 60 ismounted to the base 24. It should be understood that variousconfigurations of the caster assemblies 60 are contemplated. Inaddition, in some embodiments, the support wheels 56 are not casterwheels and may be non-steerable, steerable, non-powered, powered, orcombinations thereof. Additional support wheels 56 are alsocontemplated.

Referring to FIGS. 1 and 2 , in the illustrated embodiment, the patienttransport apparatus 20 includes an auxiliary wheel system 61 that iscoupled to the support structure 22. The auxiliary wheel system 61includes an auxiliary wheel assembly 62 that is coupled to the base 24.The auxiliary wheel assembly 62 influences motion of the patienttransport apparatus 20 during transportation over the floor surface. Theauxiliary wheel assembly 62 comprises an auxiliary wheel 64 and a liftactuator 66 operatively coupled to the auxiliary wheel 64. The liftactuator 66 is operable to move the auxiliary wheel 64 between adeployed position 68 (see FIG. 6 ) engaging the floor surface and stowedpositions 70 a, 70 b (see FIGS. 4 and 5 ) spaced away from and out ofcontact with the floor surface. The auxiliary wheel 64 influences motionof the patient transport apparatus 20 during transportation over thefloor surface when the auxiliary wheel 64 is in the deployed position68. In some embodiments, the auxiliary wheel assembly 62 comprises anadditional auxiliary wheel movable with the auxiliary wheel 64 betweenthe deployed position 68 and stowed positions 70 a, 70 b via the liftactuator 66.

By deploying the auxiliary wheel 64 on the floor surface, the patienttransport apparatus 20 can be easily moved down long, straight hallwaysor around corners, owing to a non-swiveling nature of the auxiliarywheel 64. When the auxiliary wheel 64 is stowed (see FIGS. 4 and 5 ),the patient transport apparatus 20 is subject to moving in an undesireddirection due to uncontrollable swiveling of the support wheels 56. Forinstance, during movement down long, straight hallways, the patienttransport apparatus 20 may be susceptible to “dog tracking,” whichrefers to undesirable sideways movement of the patient transportapparatus 20. Additionally, when cornering, without the auxiliary wheel64 deployed, and with all of the support wheels 56 able to swivel, thereis no wheel assisting with steering through the corner, unless one ormore of the support wheels 56 are provided with steer lock capabilityand the steer lock is activated.

The auxiliary wheel 64 may be arranged parallel to the longitudinal axis28 of the base 24. Said differently, the auxiliary wheel 64 rotatesabout a rotational axis R (see FIG. 3A) oriented perpendicularly to thelongitudinal axis 28 of the base 24 (albeit offset in some cases fromthe longitudinal axis 28). In the embodiment shown, the auxiliary wheel64 is incapable of swiveling about a swivel axis. In other embodiments,the auxiliary wheel 64 may be capable of swiveling, but can be locked ina steer lock position in which the auxiliary wheel 64 is locked tosolely rotate about the rotational axis R oriented perpendicularly tothe longitudinal axis 28. In still other embodiments, the auxiliarywheel 64 may be able to freely swivel without any steer lockfunctionality.

The auxiliary wheel 64 may be located to be deployed inside a perimeterof the base 24 and/or within a support wheel perimeter defined by theswivel axes 58 of the support wheels 56. In some embodiments, such asthose employing a single auxiliary wheel 64, the auxiliary wheel 64 maybe located near a center of the support wheel perimeter, or offset fromthe center. In this case, the auxiliary wheel 64 may also be referred toas a fifth wheel. In other embodiments, the auxiliary wheel 64 may bedisposed along the support wheel perimeter or outside of the supportwheel perimeter. In the embodiment shown, the auxiliary wheel 64 has adiameter larger than a diameter of the support wheels 56. In otherembodiments, the auxiliary wheel 64 may have the same or a smallerdiameter than the support wheels 56.

In one embodiment shown in FIGS. 2-3B, the base 24 comprises a firstcross-member 72 a and a second cross-member 72 b. The auxiliary wheelassembly 62 is disposed between and coupled to the cross-members 72 a,72 b. The auxiliary wheel assembly 62 comprises a first auxiliary wheelsupport frame 74 a coupled to and arrange to articulate (e.g. pivot)relative to the first cross-member 72 a. The auxiliary wheel assembly 62further comprises a second auxiliary wheel support frame 74 b pivotablycoupled to the first auxiliary wheel support frame 74 a and the secondcross-member 72 b. The second auxiliary wheel support frame 74 b isarranged to articulate and translate relative to the second cross-member72 b. The second cross-member 72 b defines a slot 78 for receiving a pin80 (see FIGS. 4-6 ) connected to the second auxiliary wheel supportframe 74 b to permit the second auxiliary wheel support frame 74 b totranslate and pivot relative to the second cross-member 72 b.

In some embodiments, as shown in FIGS. 3A and 3B, the auxiliary wheelassembly 62 comprises an auxiliary wheel drive system 90 (described inmore detail below) operatively coupled to the auxiliary wheel 64. Theauxiliary wheel drive system 90 is configured to drive (e.g. rotate) theauxiliary wheel 64. In the embodiment shown, the auxiliary wheel drivesystem 90 comprises a motor 102 coupled to a power source 104 (shownschematically in FIG. 9 ) and the second auxiliary wheel support frame74 b. The auxiliary wheel drive system 90 further comprises a gear train106 coupled to the motor 102 and an axle 76 of the auxiliary wheel 64.In the embodiment shown, the auxiliary wheel 64, the gear train 106, andthe motor 102 are arranged and supported by the second auxiliary wheelsupport frame 74 b to articulate and translate with the second auxiliarywheel support frame 74 b relative to the second cross-member 72 b. Inother embodiments, the axle 76 of the auxiliary wheel 64 is coupleddirectly to the second auxiliary wheel support frame 74 b.

Energy is provided from the power source 104 to energize the motor 102.The motor 102 converts energy from the power source 104 to torquesupplied to the gear train 106. The gear train 106 transfers torque tothe auxiliary wheel 64 to rotate the auxiliary wheel 64.

In the embodiment shown, the lift actuator 66 is a linear actuatorcomprising a housing 66 a and a drive rod 66 b extending from thehousing 66 a. The drive rod 66 b has a proximal end received in thehousing 66 a and a distal end spaced from the housing 66 a. The distalend of the drive rod 66 b is configured to be movable relative to thehousing 66 a to extend and retract an overall length of the liftactuator 66. The housing 66 a is pivotally coupled to the secondcross-member 72 b and the distal end of the drive rod 66 b is coupled tothe first auxiliary wheel support frame 74 a. More specifically, thefirst auxiliary wheel support frame 74 a defines a slot 82 to receive apin 84 connected to the distal end of the drive rod 66 b to permit thedrive rod 66 b to translate and pivot relative to the first auxiliarywheel support frame 74 a.

In the embodiment shown, the auxiliary wheel assembly 62 comprises abiasing device such as a torsion spring 86 to apply a biasing force tobias the first and second auxiliary wheel support frames 74 a, 74 btoward the floor surface and thus move the auxiliary wheel 64 toward thedeployed position 68 (see FIG. 6 ). The pin 84 at the distal end of thedrive rod 66 b abuts a first end of the slot 82 to limit the distancethe torsion spring 86 would otherwise rotate the first auxiliary wheelsupport frame 74 a toward the floor surface. Thus, even though thetorsion spring 86 applies the force that ultimately causes the auxiliarywheel 64 to move to the floor surface in the deployed position 68, thelift actuator 66 is operable to move the auxiliary wheel 64 to thedeployed position 68 and the stowed positions 70 a, 70 b, or any otherposition.

In the embodiment shown, in the deployed position 68 of FIG. 6 , thelift actuator 66 is controlled so that the pin 84 is located centrallyin the slot 82 to permit the auxiliary wheel 64 to move away from thefloor surface when encountering an obstacle and to dip lower whenencountering a low spot in the floor surface. For instance, when theauxiliary wheel 64 encounters an obstacle, the auxiliary wheel 64 movesup to avoid the obstacle and the pin 84 moves toward a second end of theslot 82 against the biasing force from the torsion spring 86 withoutchanging the overall length of the lift actuator 66. Conversely, whenthe auxiliary wheel 64 encounters a low spot in the floor surface, theauxiliary wheel 64 is able to travel lower to maintain traction with thefloor surface and the pin 84 moves toward the first end of the slot 82via the biasing force from the torsion spring 86 without changing theoverall length of the lift actuator 66.

Referring to FIG. 3B, the first and second auxiliary wheel supportframes 74 a, 74 b each comprise first arms pivotably coupled to eachother on one side of the auxiliary wheel 64 (as shown in FIG. 3A) andsecond arms pivotably coupled to each other on the other side of theauxiliary wheel 64. The first and second arms are pivotably connected bypivot pins. The first and second arms of the first auxiliary wheelsupport frame 74 a are rigidly connected to each other such that thefirst and second arms of the first auxiliary wheel support frame 74 aarticulate together relative to the first cross-member 72 a. The firstand second arms of the second auxiliary wheel support frame 74 b arerigidly connected to each other such that the first and second arms ofthe second auxiliary wheel support frame 74 b articulate and translatetogether relative to the second cross-member 72 b. The secondcross-member 72 b defines another slot 78 for receiving another pin 80connected to the second auxiliary wheel support frame 74 b (one for eacharm). The respective first and second arms of the first and secondauxiliary wheel support frames 74 a, 74 b cooperate to balance the forceapplied by the auxiliary wheel 64 against the floor surface.

Referring to FIGS. 4 and 5 , the auxiliary wheel 64 is in one stowedposition spaced from the floor surface. FIG. 4 illustrates oneembodiment of the auxiliary wheel 64 being in a fully stowed position 70a and FIG. 5 illustrates one embodiment of the auxiliary wheel 64 beingin a partially stowed position 70 b. In the stowed positions 70 a, 70 b,the lift actuator 66 applies a force against the biasing force of thetorsion spring 86 to retain a spaced relationship of the auxiliary wheel64 with the floor surface. To move the auxiliary wheel 64 to thedeployed position 68 (see FIG. 6 ), the distal end of the drive rod 66 bis configured to retract into the housing 66 a, which permits thebiasing force of the torsion spring 86 to rotate the first auxiliarywheel support frame 74 a, the second auxiliary wheel support frame 74 b,and the auxiliary wheel 64 toward the floor surface. The secondauxiliary wheel support frame 74 b is configured to rotate relative tothe first auxiliary wheel support frame 74 a by virtue of the secondauxiliary wheel support frame 74 b being pivotably coupled to the firstauxiliary wheel support frame 74 a (via a pinned connectiontherebetween) and pivotably and slidably coupled to the secondcross-member 72 b. In other words, the slot 78 of the secondcross-member 72 b permits the pin 80, and thus the second auxiliarywheel support frame 74 b to move toward the first cross-member 72 a. Toreturn the auxiliary wheel 64 to the stowed position, the lift actuator66 is configured to apply a force greater than the biasing force of thetorsion spring 86 to move the auxiliary wheel 64 away from the floorsurface.

Referring to FIG. 6 , the auxiliary wheel 64 is in the deployed position68 engaging the floor surface. In this embodiment, the overall length ofthe lift actuator 66 is shorter when the auxiliary wheel 64 is in thedeployed position 68 than when the auxiliary wheel 64 is in the stowedpositions 70 a, 70 b.

Although an exemplary embodiment of an auxiliary wheel assembly 62 isdescribed above and shown in the figures, it should be appreciated thatother configurations employing a lift actuator 66 to move the auxiliarywheel 64 between the stowed positions 70 a, 70 b and deployed position68 are contemplated.

In some embodiments, the lift actuator 66 is configured to ceaseapplication of force against the biasing force of the torsion spring 86instantly to permit the torsion spring 86 to move the auxiliary wheel 64to the deployed position 68 expeditiously. In one embodiment, theauxiliary wheel 64 moves from the fully stowed position 70 a to thedeployed position 68 in less than three seconds. In another embodiment,the auxiliary wheel 64 moves from the fully stowed position 70 a to thedeployed position 68 in less than two seconds. In still otherembodiments, the auxiliary wheel 64 moves from the fully stowed position70 a to the deployed position 68 in less than one second. A suitableactuator for the lift actuator 66 comprises a linear actuator suppliedby LINAK A/S located at Smedevenget 8, Guderup, DK-6430, Nordborg,Denmark. It is contemplated that any suitable actuator capable ofdeploying the auxiliary wheel 64 may be utilized.

Referring to FIGS. 7-10 , as an example, a motorized wheel in the centerof a 500 lb patient transport apparatus 20 needs 150-200 lbs of normalforce against the floor surface with a rubber 6″ auxiliary wheel toprovide the proper traction to drive the patient transport apparatus 20up a 6 degree ramp. This type of force typically requires a high-forcespring to apply the load and provide enough travel in the wheelmechanism to account for bumps or valleys in the floor surface. Withthat type of high-force spring, it can be challenging to assemble orservice the sub-assembly.

To solve these problems, the patient transport apparatus 20 includes abiasing load adjustment assembly 110 that is configured to adjust abiasing force being applied by the biasing device. In some embodiments,the biasing load adjustment assembly 110 includes a component that canbe moved with a bolt to add or relieve the load on the spring. Inaddition, the biasing load adjustment assembly 110 may include holes inone or more moving components where a pin, bolt, or tool can be used tohold the moving parts in place while a service technician is working onthe sub-assembly or removing components. In some embodiments, thebiasing load adjustment assembly 110 includes a bolt/nut that can beadjusted to relieve the load off of the actuator holding the springforce to allow a service technician to remove the actuator from thesub-assembly.

Referring to FIGS. 7-10 , in the illustrated embodiments, the auxiliarywheel assembly 62 includes a biasing load adjustment assembly 110 thatis configured to adjust a biasing force being applied by the torsionspring 86 to the auxiliary wheel 64. The torsion spring 86 is in contactwith the wheel support frame 74 a to bias the wheel support frame 74 aaway from the base 24 and to bias the auxiliary wheel 64 to the deployedposition 68. The wheel support frame 74 a is coupled to the firstcross-member 72 a and to the auxiliary wheel 64 for moving the auxiliarywheel 64 between the stowed position 70 a and the deployed position 68.

Referring to FIG. 7 , in some embodiments, the biasing load adjustmentassembly 110 includes a slider block 112 that is slideably coupled tothe first cross-member 72 a. The slider block 112 is positionable alongan outer surface 114 of the first cross-member 72 a and is configured tocontact the torsion spring 86 to adjust a load imparted on the wheelsupport frame 74 a by the torsion spring 86. The torsion spring 86extends between a first end 116 and a second end 118. The first end 116is positioned in contact with the slider block 112 and the second end118 positioning in contact with the wheel support frame 74 a.

The biasing load adjustment assembly 110 also includes a positioningbracket 120 and a positioning assembly 122. The positioning bracket 120is coupled to the first cross-member 72 a and extends outwardly from theouter surface 114 of the first cross-member 72 a. The positioningassembly 122 is coupled to the positioning bracket 120 and to the sliderblock 112. The positioning assembly 122 is configured to adjust aposition of the slider block 112 relative to the torsion spring 86 tofacilitate adjusting the load imparted on the wheel support frame 74 aby the torsion spring 86.

The positioning bracket 120 includes a positioning opening 124 thatextends through an outer surface of the positioning bracket 120 and issized and shaped to receive the positioning assembly 122 therethrough.The positioning assembly 122 extends through the positioning opening 124to contact the slider block 112. The positioning assembly 122 includes apositioning bolt 126 that extends through the positioning opening 124.The positioning bolt 126 is coupled to the slider block 112 such that alinear movement of the positioning bolt 126 causes a movement of theslider block 112 along the outer surface 114 of the first cross-member72 a.

The positioning assembly 122 also includes a positioning nut 128 that isrotatably coupled to the positioning bolt 126 to adjust a position ofthe positioning bolt 126 with respect to the positioning bracket 120.The positioning bolt 126 includes a threaded outer surface. Thepositioning nut 128 is threadably coupled to the positioning bolt 126and is configured to contact the positioning bracket 120 such that arotation of the positioning bolt 126 causes a linear movement of thepositioning bolt 126. For example, a rotation of the positioning nut 128in a first rotational direction 130 moves the positioning bolt 126towards the torsion spring 86 and a rotation of the positioning nut 128in a second rotational direction 132 moves the positioning bolt 126 awayfrom the torsion spring 86. The slider block 112 is movable along theouter surface 114 of the first cross-member 72 a in a first lineardirection 134 towards the torsion spring 86 and a second opposite lineardirection 136 away from the torsion spring 86. The rotation of thepositioning nut 128 in the first rotational direction 130 moves theslider block 112 in the first linear direction 134 towards the torsionspring 86. The rotation of the positioning nut 128 in the secondrotational direction 132 moves the slider block 112 in the secondopposite linear direction 136 away from the torsion spring 86.

During operation, an operator may rotate the positioning nut 128 in thefirst rotational direction 130 to move the positioning bolt 126 andslider block 112 in the first linear direction 134 to contact the firstend 116 of torsion spring 86 and increase a biasing force imparted bythe torsion spring 86 onto the wheel support frame 74 a and the liftactuator 66. In addition, when the operator desired to performmaintenance of the lift actuator 66, the operator may rotate thepositioning nut 128 in the second rotational direction 132 to move thepositioning bolt 126 and the slider block 112 in the second oppositelinear direction 136 away from the torsion spring 86 to reduce thebiasing load of the torsion spring on the wheel support frame 74 a andlift actuator 66.

Referring to FIG. 8 , in some embodiments, the positioning assembly 122may include a positioning pin 138 that is inserted through thepositioning opening 124 to contact the slider block 112 to maintain aposition of the slider block 112 with respect to the torsion spring 86.The positioning pin 138 may be removable to allow an operator to removethe positioning pin 138 to allow the slider block 112 to move away fromthe torsion spring 86 to reduce the biasing force being applied by thetorsion spring 86.

Referring to FIG. 9 , in some embodiments, the positioning assembly 122is coupled to the positioning bracket 120 and to the wheel support frame74 a for holding a position of the wheel support frame 74 a with respectto the first cross-member 72 a. The positioning assembly 122 includesthe positioning bolt 126 extending through the positioning opening 124and coupled to the wheel support frame 74 a such that a movement of thewheel support frame 74 a causes a movement of the positioning bolt 126.The positioning bolt 126 extends to a distal end connected to the wheelsupport frame 74 a in any suitable manner. The distal end may beconnected via a joint, such as a ball and socket joint, pivot joint,sliding joint, or the like. The connection only needs to be able totransmit a force on the positioning bolt 126 to the wheel support frame74 a so that movement of the positioning bolt 126 causes movement of thewheel support frame 74 a.

The positioning nut 128 is rotatably coupled to the positioning bolt 126to adjust a position of the positioning bolt 126 with respect to thepositioning bracket 120. In the illustrated embodiment, the positioningnut 128 is threadably coupled to the threaded outer surface of thepositioning bolt 126 such that a rotation of the positioning nut 128 inthe first rotational direction 130 moves the wheel support frame 74 a inthe first linear direction 134 away the first cross-member 72 a byvirtue of the force from the torsion spring 86, and a rotation of thepositioning nut 128 in the second rotational direction 132 moves thewheel support frame 74 a in the second opposite linear direction 136towards the first cross-member 72 a, similar to how the wheel supportframe 74 a moves when stowing the auxiliary wheel 64. The positioningassembly 122 is employed to hold the wheel support frame 74 a againstmovement toward the deployed position that could otherwise be caused bythe torsion spring 86. Accordingly, with the positioning bolt 126 beingconnected to the wheel support frame 74 a and the positioning nut 128being tightened, the wheel support frame 74 a can be held in itsposition shown in FIG. 9 and the actuator 66 can be removed for service.Once service is complete, the positioning nut 128 can be loosened enoughso that the wheel support frame 74 a is able to move normally to thedeployed position.

Referring to FIG. 10 , in some embodiments, the biasing load adjustmentassembly 110 includes a support bracket 140 that extends outwardly fromthe first cross-member 72 a towards the wheel support frame 74 a. Thesupport bracket 140 includes a positioning opening 124 that extendsthrough an outer surface of the support bracket 140. The wheel supportframe 74 a includes a positioning slot 142 that is orientated withrespect to the positioning opening 124 such that a tool 144 (e.g., pin,screwdriver, or other interference device) may be removably insertedthrough the positioning opening 124 and the positioning slot 142 toprevent a movement of the wheel support frame 74 a with respect to thefirst cross-member 72 a with the tool 144 positioned within thepositioning opening 124 and the positioning slot 142. In some cases, thepositioning slot 142 is an opening of similar shape as the positioningopening 124.

Several embodiments have been discussed in the foregoing description.However, the embodiments discussed herein are not intended to beexhaustive or limit the invention to any particular form. Theterminology which has been used is intended to be in the nature of wordsof description rather than of limitation. Many modifications andvariations are possible in light of the above teachings and theinvention may be practiced otherwise than as specifically described.

What is claimed is:
 1. A patient transport apparatus comprising: a basearranged for movement along a floor surface; an intermediate frameoperatively attached to the base and supporting a patient support deckto support a patient; an auxiliary wheel assembly including a wheelsupport frame supporting a motor and an auxiliary wheel disposed inrotational communication with the motor to influence motion of thepatient transport apparatus over the floor surface, the wheel supportframe being arranged for pivoting movement relative to the base to movethe auxiliary wheel between: a deployed position with the auxiliarywheel engaging the floor surface to drive along the floor surface, and astowed position with the auxiliary wheel spaced from the floor surface;a lift actuator operable to move the auxiliary wheel between thedeployed position and the stowed position; a biasing device arranged tourge the wheel support frame away from the base to bias the auxiliarywheel towards the deployed position; and a biasing load adjustmentassembly for adjusting a biasing force applied by the biasing device tothe auxiliary wheel.
 2. The patient transport apparatus of claim 1,wherein the biasing load adjustment assembly includes a slider blockarranged for sliding movement relative to the base and disposed incontact with the biasing device to adjust a load imparted on the wheelsupport frame by the biasing device.
 3. The patient transport apparatusof claim 2, further including a support frame operatively attached tothe base and including a first cross-member and a second cross-memberspaced a distance from the first cross-member along a longitudinal axis,with the wheel support frame pivotably coupled to the first cross-memberfor moving the auxiliary wheel between the stowed position and thedeployed position.
 4. The patient transport apparatus of claim 3,wherein the slider block is positionable along an outer surface of thefirst cross-member to contact the biasing device to adjust a loadimparted on the wheel support frame by the biasing device.
 5. Thepatient transport apparatus of claim 4, wherein the biasing loadadjustment assembly includes: a positioning bracket coupled to the firstcross-member; and a positioning assembly coupled to the positioningbracket and the slider block for adjusting a position of the sliderblock relative to the biasing device to facilitate adjusting the loadimparted on the wheel support frame by the biasing device.
 6. Thepatient transport apparatus of claim 5, wherein the positioning bracketincludes a positioning opening extending through the positioningbracket, the positioning assembly extending through the positioningopening to contact the slider block.
 7. The patient transport apparatusof claim 6, wherein the positioning assembly includes a positioning pininserted through the positioning opening to contact the slider block tomaintain a position of the slider block with respect to the biasingdevice.
 8. The patient transport apparatus of claim 6, wherein thepositioning assembly includes a positioning bolt extending through thepositioning opening defined through the positioning bracket, thepositioning bolt coupled to the slider block such that a movement of thepositioning bolt causes a movement of the slider block.
 9. The patienttransport apparatus of claim 8, wherein the positioning assemblyincludes a positioning nut rotatably coupled to the positioning bolt toadjust a position of the positioning bolt with respect to thepositioning bracket.
 10. The patient transport apparatus of claim 9,wherein the positioning bolt includes a threaded outer surface, thepositioning nut threadably coupled to the positioning bolt.
 11. Thepatient transport apparatus of claim 10, wherein a rotation of thepositioning nut in a first rotational direction moves the slider blocktowards the biasing device and a rotation of the positioning nut in asecond rotational direction moves the slider block away from the biasingdevice.
 12. The patient transport apparatus of claim 11, wherein theslider block is movable along an outer surface of the first cross-memberin a first linear direction towards the biasing device and a secondopposite linear direction away from the biasing device; and wherein therotation of the positioning nut in the first rotational direction movesthe slider block in the first linear direction towards biasing device,and the rotation of the positioning nut in the second rotationaldirection moves the slider block in the second opposite linear directionaway from the biasing device.
 13. The patient transport apparatus ofclaim 1, wherein the biasing device extends between a first end and asecond end, the first end positioned in contact with the biasing loadadjustment assembly and the second end positioned in contact with thewheel support frame.
 14. The patient transport apparatus of claim 1,wherein the biasing load adjustment assembly includes: a positioningbracket operatively attached to the base; and a positioning assemblycoupled to the positioning bracket and to the wheel support frame foradjusting a position of the wheel support frame with respect to thebase.
 15. The patient transport apparatus of claim 14, wherein thepositioning assembly includes a positioning bolt extending through apositioning opening defined through the positioning bracket, thepositioning bolt coupled to the wheel support frame such that a movementof the wheel support frame causes a movement of the positioning bolt.16. The patient transport apparatus of claim 15, wherein the positioningassembly includes a positioning nut rotatably coupled to the positioningbolt to adjust a position of the positioning bolt with respect to thepositioning bracket.
 17. The patient transport apparatus of claim 16,wherein the positioning bolt includes a threaded outer surface, thepositioning nut threadably coupled to the positioning bolt.
 18. Thepatient transport apparatus of claim 17, wherein a rotation of thepositioning nut in a first rotational direction moves the wheel supportframe towards the base and a rotation of the positioning nut in a secondrotational direction moves the wheel support frame away from the base.19. The patient transport apparatus of claim 1, wherein the biasing loadadjustment assembly includes a support bracket extending outwardly fromthe base towards the wheel support frame, the support bracket includinga positioning opening extending therethrough; and wherein the wheelsupport frame includes a positioning slot orientated with respect to thepositioning opening such that a tool may be removably inserted throughthe positioning opening and the positioning slot to prevent a movementof the wheel support frame with respect to the base.
 20. The patienttransport apparatus of claim 1, wherein the biasing device includes atorsion spring in contact with the wheel support frame to bias the wheelsupport frame away from the base.